I found that there is two WD Raptor 74GB version (8MB and 16MB cache). I would to like to get Raptor 74GB but not sure about cache size. Is cache size important? I will use it on RAID 0.
I would go for the 16MB version. Not only because of the cache (it only helps if the data you want to read is already in cache otherwise you only transfer as fast as the hard drive can read) but becuause the 16MB is the newer of the 2 and has a slightly better overall performance and I think the 16MB one also supports NCQ where the other one didn't.
Seek Times 16MB
Read Seek Time 4.6 ms
Write Seek Time 5.2 ms (average)
Track-To-Track Seek Time 0.4 ms (average)
Full Stroke Seek 10.2 ms (average)
Seek Times 8MB
Read Seek Time 4.5 ms
Write Seek Time 5.9 ms (average)
Track-To-Track Seek Time 0.6 ms (average)
Full Stroke Seek 10.2 ms (average)